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A new breakwater
Of all of the work carried out by the Department as part of the stimulation phase of Canada’s Economic Action Plan (2009–2011), one structure in particular held the attention of numerous stakeholders, both users and engineers: that of the breakwater in Grosse-Île in the Magdalen Islands.
This breakwater forms an artificial islet not attached to shore, which is rather rare. In fact, there are very few similar structures in Quebec, particularly in an area that is constantly affected by strong winds.
Why build this type of structure? “First, it was to offer protection to fishing boats when they return loaded and perform the final manoeuvres to enter the harbour,” said Yves Gingras, Chief Project Engineer at the Regional Small Craft Harbours Branch. At this particular site, the sea is agitated by strong currents and prevailing west–north-west winds. The breakwater’s exact position is not mere coincidence; agitation studies were conducted to determine the breakwater’s geometry, orientation and position.
Six metres high at its deepest section, the breakwater is nearly 60 metres long. It has been designed to intercept certain waves and reduce their strength. It is therefore entirely normal that crossing, or the ability of waves to overtake the structure, would occur.
Since the Magdalen Islands area does not have stones that are resistant enough for this construction, other stones had to be brought in from New Brunswick. Approximately seven tonnes of 2-metre wide stones were required to build this breakwater.
This project, considered daring by some because of climate constraints, was completed over a long period: fall 2010 to September 2011. The work was mainly carried out during winter, at an average of only about 10 hours per week in order not to interfere with fishing activities.
To date, comments from users seem positive. Fishers working in this area often face strong marine currents that wreak havoc on this area. It’s clear that the breakwater is doing the work it was designed for, but the real test will come in the fall, when the prevailing winds will be north-west.
Small Craft Harbours
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